An object to be viewed by a night vision device is considered to either emit or reflect a particularly characteristic spectral energy distribution (SED) under each given set of surrounding environment conditions. Such a spectral energy distribution is often referred-to as the signature of the object, the signature with respect to night vision devices. Such spectral energy distribution characteristics of a target object or a target scene are often measured for analytical purposes on a wavelength by wavelength basis, using a scanning spectroradiometer system. The results of this measurement are often then combined with characteristics of the consideration to predict the performance of the system in response to that particular target or scene--a prediction therefore involving measurements desirably accomplished in the controlled conditions of a laboratory.
In view of this cumbersome procedure, precise laboratory tests of night vision devices and other electro-optical systems are often restricted to use of a limited number of calibration standards. Reconstructing the spectral energy distribution (for example the relevant colors where visible wavelengths are involved) of the large number of objects encountered in field use of a system has heretofore been considered to be very difficult since field-encountered objects can have complex spectral energy distributions that are not easy to reproduce. The present invention however emulates either of the emissive or reflective spectral energy distribution characteristics of a wide variety of objects for use in laboratory evaluations of several classes of electro-optical sensors, particularly night vision devices.
Formally of course the term "color" relates to wavelengths in the spectral range between 400 and 700 nanometers where the human eye is responsive. Since the present invention relates to night vision equipment having principal spectral response in the near-infrared region, the spectral range between 650 and 1000 nanometers of wavelength, many of the wavelength changes of present concern can be referred-to as "color" changes only in a generic sense. Nevertheless it is the intent of the invention to provide a rapidly achievable and accurate evaluation of the spectral energy distribution response of a night vision device to predictable inputs of differing spectral content.
The U.S. patent art indicates the presence of inventive activity in the field of night vision devices and their spectral energy distribution-related testing. One such patent is U.S. Pat. No. 5,200,622 issued to J. M. Rouchon et al, a patent which is concerned with an infrared observation system having a self-checking feature. The Rouchon patent uses the Narcissus effect parasitic image which is imposed on the useful image of an aircraft pod mounted or other infrared system to achieve the self checking feature. The Rouchon patent appears to be only distally related to the spectral energy distribution testing concept of the present invention, however.
The invention of R. D. Rosenthal in U.S. Pat. No. 4,969,115 is of general background interest with respect to the present invention in the sense that it discloses use of infrared spectrum energy to achieve quantitative measurements of organic samples and also an arrangement for determining the similarity of a sequence of these organic samples. The Rosenthal apparatus is however only distally, if at all, related to night vision equipment and its spectral energy distribution testing.
The additional invention of R. D. Rosenthal in U.S. Pat. No. 5,204,532 is also of general background interest with respect to the present invention in the sense that it discloses use of near-infrared spectral calibration standards, i.e. spectral clusters of known calibration constant, to achieve accurate calibration of a blood glucose measuring system. This Rosenthal apparatus is also however only distally, if at all, related to night vision equipment spectral energy distribution testing.
Similarly the patent of J. R. Apperson et al., U.S. Pat. No. 5,206,511, is of general background interest with respect to the present invention. The Apperson et al. patent discloses an arrangement for calibrating an infrared apparatus of the blood gas analyzer type, a device of the nature used in surgical operating rooms to measure a patient's breath gasses. This calibration is achieved in the above referred-to manner of using known standard elements which have predetermined numeric values of reflection or absorption. The Apperson et al. apparatus is however, also only distally, if at all, related to night vision equipment and its spectral energy distribution testing.
The invention of P. G. Morse in U.S. Pat. No. 4,965,448 is also of general background interest with respect to the present invention in the sense that it discloses use of a calibration standard in an infrared detector system. The Morse apparatus however also appears only distally, if at all, related to night vision equipment and its spectral energy distribution testing.
The invention of J. B. Sampsell et al. in U.S. Pat. No. 5,323,002 is also of interest with respect to the present invention, since it discloses use of a calibration arrangement in an optical system. In particular the Sampsell et al. system uses a spatial light modulator to achieve a desired mix of different temperature or different color-operated calibration sources. The Sampsell apparatus also discloses the use of a two or three point calibration arrangement, output to input calibration of an optical system and storage of a generated correction factor to correct the output to input calibration. The Sampsell et al. apparatus appears only distally related to night vision equipment and its spectral energy distribution testing.
The prior patent of one inventor named in the present patent document, U.S. Pat. No. 5,070,239, issued to A. R. Pinkus, is also of interest with respect to the present invention. This patent discloses a night vision device testing arrangement which includes an input signal source and a night vision device output measuring apparatus for evaluating the tested night vision device's response to this input signal. The Pinkus apparatus also appears only distally related to night vision equipment and its spectral energy distribution testing however.
Similarly the patent of E. N. Neigoff et al., U.S. Pat. No. 5,220,840, is also of general background interest with respect to the present invention. The Neigoff et al. patent discloses an arrangement for calibrating the lamps in an accelerated weathering or colorfastness testing apparatus. This calibration is achieved with irradiation measurements of individual lamps in the sample testing area in combination with feedback control of lamp input power adjustment. The Neigoff et al. apparatus is however, also only distally, if at all, related to night vision equipment and its and its spectral energy distribution testing.
Similarly the patent of L. V. Krusewski, U.S. Pat. No. 5,122,661, is of general background interest with respect to the present invention. The Krusewski patent discloses an arrangement for testing an infrared radiation detector of the type usable in steel mills and in testing electrical contacts for heat generated by high electrical resistance, a tester employing a light emitting diode scalar output display. The Krusewski apparatus is however, also only distally, if at all, related to night vision equipment and its spectral energy distribution testing.
Similarly the patent of V. Tank et al., U.S. Pat. No. 5,311,273, is of general background interest with respect to the present invention. The Tank patent discloses an arrangement for calibrating a spectral radiometer in the infrared range of the spectrum and in the presence of atmospheric effects. The Tank et al. patent also discloses the calibration of Fourier transform spectrometers by means of complex spectral inputs. The Tank et al. apparatus is however, also only distally, if at all, related to night vision equipment and its spectral energy distribution testing with precisely known signals in a laboratory environment.
Similarly the patent of William Reitmann et al., U.S. Pat. No. 5,175,432, is of general background interest with respect to the present invention. The Reitmann patent discloses an arrangement for testing an infrared detector of the type used in satellites, a test employing an optical scene test generator which provides a representative scene and a moving object. The Reitmann et al., patent also recites in column 3, the identity of several other United States patents involving infrared sensors and their testing. The Reitmann apparatus is however, also only distally related to night vision equipment and its spectral energy distribution testing with precisely known signals in a laboratory environment.
Similarly the patent of D. E. Honigs et al., U.S. Pat. No. 5,251,006, is of general background interest with respect to the present invention. The Honigs et al. patent discloses an arrangement for calibrating a spectrophotometer which uses an absorbance standard to recalibrate a set of instrument coefficients prior to each measurement made with the instrument. The Honigs spectrophotometer instrument is concerned with both reflection and transmission measurements made in the infrared and visible portions of the electromagnetic spectrum. The Honigs apparatus is however, also only distally, if at all, related to night vision equipment and its spectral energy distribution testing.
Similarly the patent of K. E. Prager, U.S. Pat. No. 5,302,824, is of general background interest with respect to the present invention. The Prager patent discloses an arrangement for compensating gain differences in the elements of an array of optical to electrical transducers, an arrangement involving mathematical averaging and storage of correction related values in a pair of memories. The Prager apparatus is however, also only distally, if at all, related to night vision equipment and its spectral energy distribution testing.
Similarly the patent of Ian Stark et al., U.S. Pat. No. 5,237,173, is of general background interest with respect to the present invention. The Stark et al., patent discloses an arrangement for calibrating the gain of transducer devices in a scintillation camera, an arrangement which employs a plurality of individually pulsed light emitting devices. The Stark apparatus is however, also only distally, if at all, related to night vision equipment and its spectral energy distribution testing.
Similarly the patent of William Franklin et al., U.S. Pat. No. 5,302,823, is of general background interest with respect to the present invention. The Franklin et al. patent discloses an off axis collimator arrangement for monitoring the performance of an optical radiometer, a radiometer used in a photoreconnaissance space satellite. The Franklin apparatus is however, also only distally, if at all, related to night vision equipment and its spectral energy distribution testing.
The contents of three copending United States patent documents involving various combinations of the inventors named in the present document are also concerned with night vision devices and their spectral response testing and may therefore be of general interest with respect to the present invention; these documents are identified with the titles and serial numbers of "Synthetic Color Night Vision", application Ser. No. 08/498,449; "Night Vision Device Automated Spectral Response Determination", application Ser. No. 08/491,390; and "Night Vision Device Wavelength Test Pattern", application Ser. No. 08/500,302; respectively. The contents of these documents is hereby incorporated by reference into the present patent document.